Singh Papu, Sweta Singh, B. R. Singh
Abstract: The proper drying techniques are the most important aspect of leafy vegetable preservation. The use of solar dryer helps to reduce the losses and improves the quality of product. Fresh amaranth leaves were pretreated in two ways viz. (i) dipping in a solution (leaves to water 1: 5 (w/w) ) containing 0.1 % Mgcl2 + 0.1 % NaHCO3 + 2 % KMS (T1) in distilled water for 15 minute and (ii) blanching in boiling water (T2) containing 3 % sodium bisulphate for 2 min. The leaves were dried at 1.5, 2.0 and 2.5 kg/m2 loading density, under greenhouse type solar dryer and in open sun. Untreated samples (T3) were also dried as control samples. The samples were dried from initial moisture content of 655.35 to 727.12 % db to a final moisture content of 5.381 to 5.79 % db. Total drying time considerably reduced with the increase in drying air temperature from 300C under open sun drying to 44 0C under greenhouse type solar drying conditions. Major drying took place in falling rate period. The average drying rate increased with increase in temperature and decrease with time and loading density. Chemically treated samples dried under greenhouse type solar dryer took lesser time than blanched and untreated samples. It was observed that total moisture loss increased with increase in drying temperature and decreased with decrease in drying temperature. The product quality was found to be most acceptable of garlic leaves treated in the solution of 0.1 % Mgcl2 + 0.1 % NaHCO3 + 2 % KMS (T1) dried under GSD using 2.0 kg/m2 loading density.
Keywords: Loading Density, Pretreatment, Open Sun Drying, Greenhouse Type Solar drying